The present invention relates to a chopping machine.
The chopping machines used in the production of small-dimensioned wood are generally divided into two different classes according to their method of crosscutting the timber. One class comprises chopping machines in which the trunks or timbers are crosscut by slashing or shearing, while the other class comprises chopping machines that saw the timber in some way or other. In general, in slashing or shearing-type chopping machines, the splitting of the block of wood is performed simultaneously with the crosscutting, and the treatment gives the cut surfaces a somewhat uneven, unclean and untidy appearance. For this reason, these machines are not favored especially in commercial production of small-dimensioned wood.
Sawing-type chopping machines, which generally use either a chain saw or a circular saw to crosscut the timber, produce cleaner and more accurately cut material. However, the same saw blade cannot be used for splitting the timber, so these machines are generally either used in conjunction with a separate splitting apparatus or the piece cut off the timber is allowed to fall into a feeder from which it is pushed by a suitable ram through a splitting blade.
The problem with sawing-type chopping machines is that they are slow in operation and difficult and laborious to use. The timbers generally have to be fed manually to the crosscutting device, and in the splitting apparatus placed after it the blocks of wood often have to be guided manually or at least the apparatus requires continuous supervision.
U.S. Pat. No. 3,862,651 describes a chopping machine representing prior-art technology. In this solution, a chain saw is used as a crosscutting device and the feeder used to pass the timber to the crosscutting device is a long trough-like structure with a conveyor belt on its bottom. The conveyor belt is connected to the ram of a splitting apparatus so that, after pushing the block of wood to be split through the splitting blade, the ram engages the conveyor belt during its return movement, thus moving the timber to be crosscut a certain distance forward to the crosscutting device.
The equipment described in the patent is a workable solution as regards its basic idea, but it has certain drawbacks that make it commercially non-viable. First, a large proportion of the timbers to be chopped into small-dimensioned wood have curvatures, curved parts and boughs or branches. Such a timber will not move forward in the feeder according to the patent but only rests on the edges of the trough. Thus, the material has to be fed into this apparatus purely manually. Further drawbacks are the complexity of the equipment and the consequent poor durability. In practical work and in varying working conditions, the timbers are not neatly placed into the trough serving as a feeder; instead, they are more or less thrown or dropped into it. Therefore, the entire structure of the trough must be as simple and durable as possible. The conveyor belt on the bottom of the trough according to the patent does not meet these requirements.
The object of the invention is to eliminate the problems referred to above. A specific object of the invention is to disclose a new type of chopping machine that has a very simple, durable and reliable construction that allows a maximum degree of automation in the handling of wood in sawing-type chopping machines.
The chopping machine of the invention comprises a crosscutting device for cutting a timber across the grain. The crosscutting device is preferably a chain saw driven either hydraulically or by a motor, but it is also possible to use e.g. a circular saw blade. Moreover, the chopping machine comprises a feeder for feeding the timber longitudinally to the crosscutting device, said feeder comprising two elongated supporting surfaces forming a substantially horizontal trough open in the upward direction, in which the timber to be treated can be placed. In addition, the chopping machine comprises a splitting apparatus operated by a splitting cylinder for splitting a block of wood cut off a timber. According to the invention, one of the elongated supporting surfaces is connected to a suitable power means so that the supporting surface can be moved back and forth in the longitudinal direction of the trough formed by the supporting surfaces, i.e. in lengthways direction of the timber to be crosscut. In addition, according to the invention, both supporting surfaces are provided with directional holding elements on the inner surfaces of the trough, arranged in its longitudinal direction to prevent the timber in the trough from moving in relation to the surface away from the crosscutting device. In other words, the holding elements are so directed in the longitudinal direction of the trough that the timber placed upon them can slide over them in one direction but cannot move in relation to the holding elements in the other direction. Thus, as the supporting surfaces are moving longitudinally back and forth in relation to each other, the holding elements in the supporting surfaces alternately hold the timber immovable in relation to the respective supporting surface while the timber is sliding in relation to the other supporting surface. In this way, the back-and-forth movement of the supporting surfaces causes the timber to move in the hold direction of the holding elements.
In a preferred case, the splitting cylinder of the splitting apparatus is used as a power means for moving the movable supporting surface. This makes it possible for the timber to be already moved forward to the position required for the next crosscutting action while the previous piece cut off is being split.
The holding elements are preferably so disposed that they cover substantially the entire area of both supporting surfaces. Therefore, it is not necessary that the timber being treated should rest on the supporting surfaces throughout its length or the length of the supporting surfaces; instead, e.g. in the case of a curved timber, even a less perfect contact with the supporting surfaces will be enough to ensure a sufficient grip to move the timber forward. The holding element preferably consists of a projection or tongue protruding from the supporting surface and extending toward the crosscutting device, the extremity of said projection or tongue forming a sharp edge suitably directed. Thus, the holding elements may be relatively small, round or angular, scale-like or prong-like elements or longer transverse edges. An essential feature of the holding elements is that their hold or grip on the timber is considerably better in one direction than in the other direction.
The movable supporting surface and the splitting cylinder are preferably connected via a coupling that allows the splitting movement for splitting the block of timber to be made longer than the timber feed motion. This is preferably implemented by using a coupling that comprises a backlash allowing the splitting cylinder to move through a distance while the supporting surface remains immovable. Thanks to this construction, there is always in the splitting apparatus a space longer than the piece to be cut off the timber for the piece to fall into. Therefore, neither end of the piece will remain supported so as to keep the piece in an oblique position, but the piece will always fall into a space long enough to allow it to rest throughout its length on the bottom of the space in a straight position. This guarantees that the splitting apparatus will work properly and that the piece of timber to be split is always in the correct position when pushed into the splitting blade.
In the chopping machine of the invention, it is also possible to use an arrangement that allows an alternating motion of both supporting surfaces. In this case, while one surface is moving forward, the other one is moving backward, resulting in a very fast timber feed action. In particular, when a splitting apparatus with two splitting rams placed side by side is used, the motion of one splitting ram can be coupled to a first supporting surface and the motion of the other splitting ram to a second supporting surface. In this way, the feeding, crosscutting and splitting of the timber can be implemented as a fast and continuous process.
As compared with prior art, the chopping machine of the invention has significant advantages. In the invention, the action of feeding the timber to the crosscutting device is implemented using a very simple and reliable arrangement that comprises no complex parts or parts susceptible to damage. Thus, the handling of the timber is made as easy and simple as possible, in other words, the timber need not be separately fed to the crosscutting device; instead, just placing or even throwing the timber into the feed trough formed by the supporting surfaces is sufficient. Likewise, by virtue of the simple structure and reliability of the crosscutting device, feed device and splitting apparatus and the co-ordination of their operation, the whole apparatus can be relatively easily automated so as to achieve a chopping machine that, like the shearing-type machines used at present, will carry out the entire chopping process automatically after a timber is given to the machine.